Autonomous vehicles, the cruise control of which is autonomously performed by an autonomous driving system, have been developed recently. Such an autonomous vehicle determines the conscious level of the driver by testing the consciousness of the driver during the autonomous driving control. Japanese Patent Application Publication No. Hei 11-185200 discloses a conventional method for determining the conscious level of a driver in a vehicle capable of autonomous cruise control.
The driver conscious level determination method disclosed in Japanese Patent Application Publication No. Hei 11-185200 gives a test item to the driver after a lapse of a predetermined driving time and determines the conscious level of the driver by evaluating a response to the test item.
In this regard, during the autonomous driving control, the driver of the autonomous vehicle entrusts the driving to the autonomous driving system, and is highly likely not to recognize the surroundings or know the state of the vehicle, which the driver always does when manually driving the vehicle. However, an autonomous vehicle may switch from the autonomous driving control to the manual driving control when the driver is in such a state. The driver is therefore required to be always ready to take over the driving from the autonomous driving system.
The conventional driver conscious level determination method described above merely determines whether the driver is conscious, and therefore cannot determine whether or not the driver can actually take over when the autonomous driving control is switched to the manual driving control.